The present invention relates to a processing unit for photosensitive materials which are exposed imagewise, and more especially to a unit for processing printing plates. The unit has at least two treatment zones in which are located removable tank inserts which contain transport and guide devices for the continuous arcuate and linear guidance of the material through the treatment zones. In the first treatment zone there is a developing device having a cover which projects partially into the treatment fluid.
Known developing units having trough-shaped immersion baths in a double-chamber combination can be used, in general, as continuous-feed table units or as floor-standing units for the fully automatic developing of photographic papers, printing plates or the like. In such use, the difficulty often arises that the materials to be developed are curved undesirably and have scratches on the top side and/or bottom side after they have passed through the apparatus. In addition, the degree of developing is not satisfactory. In the case of continuous use for a relatively long time, the treatment baths frequently also start to foam, so that developing has to be interrupted in order to change the developer and add anti-foam agents, or the processing speed has to be reduced. It also happens frequently that the processed materials leave the unit still wet, that is to say not sufficiently squeezed out, so that a further drying step is still required.
To avoid these disadvantages, German Utility Model No. 8,028,682 proposes a developing unit having a two-tank combination, in which a rotating brushing roller having a resiliently mounted counter-roller is located in front of the outflow region of the developer tank, the brushing roller being covered by a protective hood, the rear bottom edge of which, seen in the feed direction, extends to below the level of the developer fluid. For transporting the material through the two tanks, in addition to the pairs of transport rollers, the unit includes rotatable deflecting rollers on the sensitized side and fixed guide means on the rear side. In the transition region between the developer tank and aftertreatment tank, the unit contains pairs of run-out and run-in rollers which guide the treated material by means of deflecting rollers in such a way that its rear surface does not graze the separating wall between the two tanks, with the result that undesirable scratching on the processed material is avoided.
U.S. Pat. No. 3,732,808 discloses a developing apparatus for offset printing plates which includes devices, by means of which both sides of one offset printing plate or one side each of two individual offset printing plates, resting back-to-back against one another, can be developed at the same time. The developing unit incorporates devices which simultaneously apply developer solution to the surfaces of the printing plate located opposite one another, and also brushing devices which simultaneously brush the two surfaces so as to assist the chemical reaction of the developer solution, as well as washing devices for removing the developer solution from the opposing surfaces of the printing plate, and drive devices for transporting the printing plate through the unit. The unit does not make use of an immersion bath in the developer part, so that the printing plate can be guided through the unit in a straight line. Only developing and cleaning steps are possible, but not preservation.